In railroad yards the engines are often remotely controlled to effect movement of the engine from one place to another within the yard. Depending on the location of the engine the control station may be at a distance from the engine where any malfunction of the engine or any of the cars being moved by the engine cannot be readily detected. As a result, where the engine or some other part of the train derails, the derailment may go undetected for some time resulting in substantial damage to the track as well as the engine and remainder of the train.
Detectors have been available to detect damaged rolling stock and in some cases to stop the train for repair or to otherwise appraise the damage. An example of this is the U.S. Pat. No. 2,007,800 to Graf which refers to a system that may bring a train to a halt upon sensing of the damaged rolling stock. In the preferred embodiment, however, the description is directed simply to signaling the crewman who would stop the train of their own volition. An electrical circuit is included in this system which maintains an electrical source integrated with a solenoid to prevent a switch from closing which controls a signal to stop the train. A part of the circuit includes a conductor mounted on a vertical member between the rails of the track. This vertical member is of a substance capable of being destroyed when struck by a violent blow. Thus, where a damaged part of the train extends sufficiently from the train to strike the vertical member, the circuit will be broken thereby de-energizing the solenoid allowing the switch to close. This in turn provides a signal imparted to the crew members that the train should be stopped.
The U.S. Pat. No. 746,499 to Guerin relates to an automatic system for stopping trains. The system disclosed includes a frangible device carried by the train to detect obstacles on the track and upon detection of such an obstacle to stop the train. Similar systems are disclosed in U.S. Pat. No. 1,012,493 to Willison and Wright and U.S. Pat. No. 1,200,339 to Graham and Farris. In all of these disclosures, the sensing device is actually carried by the engine or train itself.
The U.S. Pat. No. 1,372,122 to Dawson relates to an automatic train stop which is incorporated into an electrical circuit to stop the train when the engineer has failed to do so upon being appropriately signalled by a semaphore or the like. The Dawson device includes a mechanism located adjacent the rails having a frangible member which engages a switch arm for maintaining a switch in an open position unless the train fails to stop as required by the signal. The switch arm is actuated by a stop member located adjacent the track. In this way when the train goes beyond a predetermined point it engages the stop member forcing the switch arm to brake the frangible member allowing the switch to be closed which shuts down the engine. However, the Dawson device merely goes into operation when the signal is activated by some other source giving visual indication to an operator that the train should be stopped.
Another system relating to railway signaling for monitoring worn wheels includes the U.S. Pat. No. 3,546,448 to Pelino. The Pelino patent discloses a detector placed adjacent to the tracks at a position where a worn wheel will strike the detector causing it to vibrate. These vibrations are sensed and delivered to an appropriate indicator so that the operator can see that certain wheels of the train are worn and should be replaced. It should be noted that these detectors require special casing when placed adjacent to the tracks so that they will not be operated by simple virbration caused by the rolling stock. This Pelino system is unusually sophisticated in the manner in which it senses the worn wheels. Due to this complexity a substantial amount of time will be required to place the detector in the correct location. Further, there is no disclosure in Pelino of incorporating any such system to stop a train automatically.
In general these sensing devices presently available and discussed above are the frangible type which are subject to vandalism or other inadvertent fracture. Others include devices carried by the train itself and are not particularly conducive to sensing derailment of the non-frangible type, they are often so complex as to be impractical for use in sensing derailments. In addition, many of these devices are used to simply signal a crewman rather than actually shutting the engine off. Others do not provide sufficient protection from the elements to insure that the mechanism will work properly even after exposure for long periods of time.